Vacuum operable units for use with ignition distributors

ABSTRACT

A vacuum-operable unit for use with an ignition distributor in which a casing is divided into first and second chambers by a resilient diaphragm. A plunger is slidably received in the first chamber, with the plunger being secured at one end to the diaphragm and extending at its other end from the first chamber for connection to a distributor. Axial movement of the plunger varies the ignition timing of the distributor. First and second conduits are provided in communication with the first and second chambers respectively, and resilient means within one of the chambers resists movement of the diaphragm in a direction to reduce the volume of that chamber. Sealing means acts between the wall of the first chamber and the plunger to fill the first chamber while allowing relative movement between the plunger and the wall of the first chamber, with the sealing means being constituted by a pair of annular members secured to the plunger and the wall of the chamber respectively, and interconnected by a flexible tubular member. The diameter of the flexible tubular member of the sealing means tapers from a maximum diameter adjacent one annular member to a minimum diameter adjacent of the other annular members and the tubular member is turned inside out intermediate its ends so that part of the tubular member surrounds a further part of the member, and the tubular member together with said annular members constitutes a rolling seal.

[ 1 Mar. 21, 1972 [54] VACUUM OPERABLE UNITS FOR USE WITH IGNITIONDISTRIBUTORS William Harold Cooksey, Walsall, England [73} Assignee:Joseph Lucas (Industries) Limited, Birmingham, England [22] Filed: Oct.3, 1969 [21] Appl.N0.: 863,504

[72] Inventor:

[30] Forelgn Application Priority Data Oct. 14, 1968 Great Britain..48,524/68 [52] US. Cl. ..123/ll7 A [51] Int. Cl ..F02p 5/04 [58] FieldofSearch ..123/117.1;72/18.2;92/98 [56] References Cited UNITED STATESPATENTS 2,087,339 7/1937 Arthur ..123/117.1 2,383,898 8/1945 Udale ..l/72,178,953 11/1939 Chi1ton.... ..92/98 3,187,848 6/1965 Shellhause..74/18.12 3,31 1,029 3/1967 Kimble ..92/100 3,381,591 5/1968 Toschkoff..92/l68 3,426,737 2/1969 Walker 123/117 A 3,439,913 4/1969 Kamman..74/18 2 3,456,663 7/1969 Walker 123/117 A OTHER PUBLICATIONSEngineering with Sirvene, Chicago Rawhide Manufacturing Co., 1946, pp.10- 12 and 30, 31 Chemical Names, Hycar, 1945, pp. 4, 5, 7

Primary Examiner-Mark M. Newman Assistant Examiner-Ronald B. CoxAttorney-Holman & Stern [57] ABSTRACT A vacuum-operable unit for usewith an ignition distributor in which a casing is divided into first andsecond chambers by a resilient diaphragm. A plunger is slidably receivedin the first chamber, with the plunger being secured at one end to thediaphragm and extending at its other end from the first chamber forconnection to a distributor. Axial movement of the plunger varies theignition timing of the distributor. First and second conduits areprovided in communication with the first and second chambersrespectively, and resilient means within one of the chambers resistsmovement of the diaphragm in a direction to reduce the volume of thatchamber. Sealing means acts between the wall of the first chamber andthe plunger to fill the first chamber while allowing relative movementbetween the plunger and the wall of the first chamber, with the sealingmeans being constituted by a pair of annular members secured to theplunger and the wall of the chamber respectively, and interconnected bya flexible tubular member. The diameter of the flexible tubular memberof the sealing means tapers from a maximum diameter adjacent one annularmember to a minimum diameter adjacent of the other annular members andthe tubular member is turned inside out intermediate its ends so thatpart of the tubular member surrounds a further part of the member, andthe tubular member together with said annular members constitutes arolling seal.

2 Claims, 2 Drawing V VACUUM OPERABLE UNITS FOR USE WITH IGNITIONDISTRIBUTORS This invention relates to vacuum operable units for usewith ignition distributors.

A unit according to the invention includes a casing, a diaphragmdividing the easing into first and second chambers, a plunger slidablyreceived in the first chamber, the plunger being secured at one end tothe diaphragm and extending at its other end from the first chamber forconnection to the distributor, so that axial movement of the plungervaries the ignition timing of the distributor, first and second conduitscommunicating with the first and second chambers respectively, resilientmeans within one of the chambers for resisting movement of the diaphragmin a direction to reduce the volume of said one chamber, and sealingmeans acting between the wall of the first chamber and the plunger toseal to the first chamber while allowing relative movement between theplunger and the wall of the first chamber, said sealing means beingconstituted by a pair of annular members secured to the plunger and thewall of the chamber respectively, and interconnected by a flexibletubular member the diameter of which tapers from a maximum adjacent oneof said annular members to a minimum adjacent the other of said annularmembers, the tubular member being turned inside out intermediate itsends so that part of the tubular member surrounds a further part of thetubular member and the tubular member together with said annular membersconstitute a rolling seal.

The invention further resides in an ignition distributor for a roadvehicle, having combined therewith a unit as described in the precedingparagraph.

The invention still further resides in an ignition timing control systemfor a road vehicle utilizing a unit as described above.

One example of the invention is illustrated in the accompanying drawingswherein FIG. 1 is a diagrammatic sectional view of an ignitiondistributor and its associated ignition timing control system, and

FIG. 2 is an enlarged sectional view of the tapered rolling seal shownin FIG. 1.

Referring to the drawings, the distributor includes a casing 11 havingrotatable therein an axially extending shaft 12, the periphery of whichdefines a cam 13. Surrounding the shaft 12 and mounted for angularmovement with respect to the shaft 12 is an annular plate 14. The plate14 carries fixed and the movable contacts 15, 16 respectively of acontact breaker assembly, with the movable contact 16 being carried by acam follower 17. The cam follower 17 engages the cam 13, and rotation ofthe shaft 12 serves to operate the contact breaker by opening andclosing the contacts 15, 16 while angular movement of the plate 14serves to adjust the timing of the contact breaker and consequently theignition timing of the engine.

A vacuum unit 18 is mounted on the casing 11 with the unit 18 comprisinga hollow two part housing 19, 20 which is divided into two chambers 21,22 by a flexible diaphragm 23. The periphery of the part 20 of thehousing is rolled over the periphery of the part 19 to secure the parts19, 20 together, and the periphery of the diaphragm 23 is trappedbetween the peripheries of the parts 19, 20. The part 19 of the housingis formed with a stepped bore 25 which is of reduced diameter at itsouter end. A plunger 26 is axially movable in the narrower part of thebore 25, and the plunger 26 is formed at its inner end with a flange 26aand a spigot 26b. The spigot 26b extends through a first washer 31a, ahole in the diaphragm 23 and a second washer 31b with the free end ofthe spigot 26b being spread to trap the diaphragm 23 between the washers31a, 31b. The outer end of the plunger 26 is connected to the plate 14of the contact breaker assembly. Thus movements of the diaphragm 23 willbe transmitted by the plunger 26 to the plate 14 to adjust the ignitiontiming of the engine. The plunger 26 is urged inwardly by a spring 27which acts at one end against the washer 31a and at the other endagainst an annular member 28a at one end of a tapered flexible rollingseal 28. The member 28a of the seal 28 is trapped by the spring 27 insealing engagement with a shoulder defined between the wider andnarrower parts of the bore 25 and the end of the seal 28 remote from themember 28a, includes an annular member 28b which sealingly engages theplunger 26 so that the seal 28 seals the chamber 21 throughout the rangeof movement of the plunger 26. The rolling seal 28 is molded in aflexible material which is impervious to air, and includes the annularmembers 28a, 28b and tubular member 30, integral with, andinterconnecting the annular members 28a, 28b. The diameter of the member30 tapers from a maximum adjacent the annular member 28a to a minimumadjacent the annular member 28b. The plunger 26 extends through themember 28b and the diameters of the member 28b and the plunger are suchthat the annular member 28b grips, and makes sealing engagement with theplunger. Intermediate its ends, the tubular member 30 is turned insideout, so that a portion 30a of the tubular member 30 surrounds, andextends generally coaxially with, a further portion 30b of the tubularmember 30. In use, as the plunger of the vacuum unit moves axiallyrelative to the casing, the annular member 28b is caused to moverelative to the annular member 28a and so the lengths of the portions30a, 30b of the tubular member 30 are varied as the tubular member 30 isrolled back upon itself to permit the relative axial movement. It willbe appreciated, that since the tubular member 30 tapers, then duringsaid relative axial movement of the annular members the inner surface ofthe portion 300 of the member 30 is always spaced from the outer surfaceof the portion 30b thereby eliminating friction between the surfaces ofthe seal, which would otherwise tend to damp, and impede the movement ofthe plunger 26.

It has been found that there is an optimum taper angle for the member 30of the seal 28, which depends upon the material from which the seal ismanufactured. For the material is produced by Lucas Ebonite Ltd. andknown as synthetic rubber nitrile 6-18-17, synthetic rubber nitrile6-l8-54, and neoprene 6-18-57, the optimum taper angle of the plate 14lies in the range 7to 11.

The unstressed condition of the diaphragm 23, that is to say, thecondition of the diaphragm when the chambers 21, 22 are both subject toatmospheric pressure, corresponds to the normal zero ignition advanceposition of the plate 14 of the distributor. It will be appreciated thatthe normal zero advance position of the distributor does not necessarilycorrespond to a condition in which the engine with which the distributoris associated is tired at top dead center. The normal zero advanceposition of the distributor will correspond to the degree of ignitionadvance or retard the ignition by means of the vacuum unit.

A further plunger 29, coaxial with the plunger 26 is slidably receivedby the part 20 of the housing. The plunger 29 extends at one end througha central hole in an annular plate 24 towards the washer 31. Acylindrical sleeve 33 extends coaxially with the plunger 29, through thehole in the plate 24. At its end adjacent to the washer 31, the sleeve33 is formed with an inwardly directed peripheral flange 34 and at itsopposite end the sleeve 33 includes an outwardly directed peripheralflange 35 the diameter of which is greater than that of the hole in theplate 24. The plunger 29 is formed at its end adjacent the washer 31with an outwardly directed flange 32, and a spring 36 acts between theflange 32. The part 20 of the housing urges the plunger 29 towards thewasher 31, movement of the plunger 29 towards the washer 31 beinglimited by engagement of the flange 32 of the plunger 29, with theflange 34 of the sleeve 33 and engagement of the flange 35 of the sleeve33 with the plate 24.

The chamber 22 is connected by way of a conduit 37 to the air inlet sideof a throttle valve 38 of a carburetor 39 associated with the engine,and is further connected by way of a conduit 40 to a two position spoolvalve 44. Moreover, a further conduit 41 serves to connect the chamber21 to the valve 44. The valve 44 is operated automatically, for example,in response to the pressure in an inlet manifold 42 of the engine, so asto occupy a first position when the pressure in the manifold 42 risesabove a first predetermined value and to move to a second position whenthe pressure in the manifold 42 falls below a second predeterminedvalue. In its first position, the valve 44 closes the conduit 40 andconnects the conduit 41 to atmosphere, thereby subjecting the chamber 22to the pressure conditions at the air inlet side of the throttle valve38 and opening the chamber 21 to atmosphere. In its second position thevalve 44 connects the conduit 40 to atmosphere and connects the conduit41 to the manifold 42, thereby opening the chamber 22 to atmosphere andsubjecting the chamber 21 to the pressure conditions at the manifold 42.

The operation of the system is as follows. When the engine of thevehicle is inoperative, the pressure in the manifold 42 will beatmospheric pressure and the valve 44 will be in its first position.Thus, the chambers 21, 22 will both be at atmospheric pressure, and thediaphragm 23 will be in its rest position. With the engine idling, andthe throttle valve 38 closed, the pressure in the manifold 42 dropsbelow the second predetermined value and the valve 44 moves to itssecond position to subject the chamber 21 to the manifold pressure andto open the chamber 22 to atmosphere. Since the throttle valve 38 isclosed, the percentage of noxious products in the exhaust of the engineincreases and therefore the air supply to the cylinders is increased toincrease the combustion of these products. However, the resultantincrease in engine speed is reduced since the pressure differencebetween the chambers 21, 22 moves the diaphragm 23 and the plunger 26 tothe left as seen in the drawing until the washer 31a on the plunger 26engages a stop 19a integral with the part 19 of the housing. Themovement of the plunger 26 from its rest position to the left serves tomove the plate 14 angularly in a direction to retard the ignition timingof the engine thereby slowing the speed in known manner. During normaloperation of the engine, the throttle valve 38 is open and the pressurein the manifold 42 rises above the first predetermined value and thevalve 44 moves to its first position to open the chamber 21 toatmosphere and to subject the chamber 22 to the pressure at the airinlet side of the throttle valve 38.

The pressure difference between the chambers 21, 22 is now such that thediaphragm 23 is moved from its rest position to the right as seen in thedrawing thereby moving the plunger 29 against the action of the spring36. In this condition, the unit 18 acts in a convenient manner tocontrol the ignition timing of the engine. As the pressure at the airinlet side of the throttle valve 38 varies, the position of thediaphragm 23 varies correspondingly and movements of the diaphragm 23move the plate 14 in a direction to advance the ignition timing of theengine, or to retard the ignition timing from an advance setting backtowards the zero advance setting.

It will be appreciated that the position of the plate 24, the axiallength of the sleeve 33 and the rating of the spring 36 together definethe minimum pressure difference which must exist between the chambers21, 22 before there is any movement of the diaphragm 23 and consequentlythe plate 14, in the advance direction.

Assuming now that the throttle valve 38 is closed when the engine isrunning at speed and driving a load, then an overrun condition isestablished wherein the pressure in the manifold 42 drops below thesecond predetermined value and there is consequently a high percentageof noxious products in the exhaust of the vehicle. The valve 44 moves toits second position and the pressure in the manifold 42 is applied tothe chamber 21 thereby retarding the ignition timing of the engine tominimize the loss of engine braking which occurs when the air supply tothe engine is increased to cut down the percentage of noxious productsin the exhaust.

lt will be appreciated that the unit 18 will be adjustably mounted onthe casing 11, so that the ignition timing of the engine can be adjustedmanually, for example, during assembly and maintenance.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. An ignition timing control system for use in an ignition distributorfor a road vehicle said distributor including a casing, a shaftjournaled for rotation within said casing and including a cam, a platemovable angularly within the casing relative to said shaft, a contactbreaker assembly carried by said plate and operable in response torotation of said shaft and a vacuum operable unit carried by saidcasing, said unit comprising a casing, a diaphragm dividing said unitcasing into first and second chambers, a plunger slidably received inthe first chamber, the plunger being secured at one end to the diaphragmand extending at its other end from the first chamber, first and secondconduits communicating with the first and second chambers respectively,first resilient means within the first chamber and acting on thediaphragm to resist movement of the diaphragm in a direction to reducethe volume of the first chamber, second resilient means in the secondchamber, and acting on the diaphragm in a direction to resist movementof the diaphragm in a direction to reduce the volume of the secondchamber, the first and second resilient means acting on the diaphragm sothat the diaphragm is urged by the first and second resilient means to arest position corresponding to the normal zero advance position of thedistributor, stop means associated with the second resilient means inthe second chamber, the stop means preventing said second resilientmeans acting on the diaphragm during reduction in volume in the firstchamber, and sealing means acting between the wall of the first chamberand the plunger to seal the first chamber, the sealing means allowingrelative movement between the plunger and the wall of the first chamber,and including first and second annular members secured to the plungerand to the wall of the first chamber respectively, and a flexibletubular member interconnecting the first and second annular members, thediameter of the tubular member tapering from a maximum adjacent one ofthe annular members to a minimum adjacent the other of the annularmembers, and the tubular member being turned inside out intermediate itsends so that part of the tubular member surrounds a further part thereofand the tubular member together with the first and second annularmembers define a rolling seal, the plunger of said unit being connectedto said plate so that axial movement of the plunger varies the ignitiontiming of the distributor, and a valve operable in a first position,during normal running of the engine of the vehicle, to connect one ofsaid chambers to atmosphere while connecting the other chamber to theair inlet side of a throttle valve of the engine, so that variations inpressure at the air inlet side of the throttle valve serve through theunit to control the ignition timing of the distributor to advance theignition timing of the distributor from, or retard the ignition timingof the distributor to, said normal zero advance position and operable ina second position, during idling or overrun conditions of the engine, toconnect said one chamber to an inlet manifold of the engine whileconnecting the other chamber to atmosphere so that the reduced pressurein the inlet manifold serves through said unit, to retard the ignitiontiming of the distributor from said normal zero advance position.

2. The system as claimed in claim 1 wherein said valve is operated inresponse to variations in pressure in the inlet manifold of the engine,the valve being moved from its second position to its first positionwhen the pressure in the inlet manifold of the engine rises above afirst predetermined value and the valve being moved from its firstposition to its second position when said pressure falls below a secondpredetermined value.

1. An ignition timing control system for use in an ignition distributorfor a road vehicle said distributor including a casing, a shaftjournaled for rotation within said casing and including a cam, a platemovable angularly within the casing relative to said shaft, a contactbreaker assembly carried by said plate and operable in response torotation of said shaft and a vacuum operable unit carried by saidcasing, said unit comprising a casing, a diaphragm dividing said unitcasing into first and second chambers, a plunger slidably received inthe first chamber, the plunger being secured at one end to the diaphragmand extending at its other end from the first chamber, first and secondconduits communicating with the first and second chambers respectively,first resilient means within the first chamber anD acting on thediaphragm to resist movement of the diaphragm in a direction to reducethe volume of the first chamber, second resilient means in the secondchamber, and acting on the diaphragm in a direction to resist movementof the diaphragm in a direction to reduce the volume of the secondchamber, the first and second resilient means acting on the diaphragm sothat the diaphragm is urged by the first and second resilient means to arest position corresponding to the normal zero advance position of thedistributor, stop means associated with the second resilient means inthe second chamber, the stop means preventing said second resilientmeans acting on the diaphragm during reduction in volume in the firstchamber, and sealing means acting between the wall of the first chamberand the plunger to seal the first chamber, the sealing means allowingrelative movement between the plunger and the wall of the first chamber,and including first and second annular members secured to the plungerand to the wall of the first chamber respectively, and a flexibletubular member interconnecting the first and second annular members, thediameter of the tubular member tapering from a maximum adjacent one ofthe annular members to a minimum adjacent the other of the annularmembers, and the tubular member being turned inside out intermediate itsends so that part of the tubular member surrounds a further part thereofand the tubular member together with the first and second annularmembers define a rolling seal, the plunger of said unit being connectedto said plate so that axial movement of the plunger varies the ignitiontiming of the distributor, and a valve operable in a first position,during normal running of the engine of the vehicle, to connect one ofsaid chambers to atmosphere while connecting the other chamber to theair inlet side of a throttle valve of the engine, so that variations inpressure at the air inlet side of the throttle valve serve through theunit to control the ignition timing of the distributor to advance theignition timing of the distributor from, or retard the ignition timingof the distributor to, said normal zero advance position and operable ina second position, during idling or overrun conditions of the engine, toconnect said one chamber to an inlet manifold of the engine whileconnecting the other chamber to atmosphere so that the reduced pressurein the inlet manifold serves through said unit, to retard the ignitiontiming of the distributor from said normal zero advance position.
 2. Thesystem as claimed in claim 1 wherein said valve is operated in responseto variations in pressure in the inlet manifold of the engine, the valvebeing moved from its second position to its first position when thepressure in the inlet manifold of the engine rises above a firstpredetermined value and the valve being moved from its first position toits second position when said pressure falls below a secondpredetermined value.